Jooo -- thanks for that info. So it's really like maneuvoring a sofa cleverly through a narrow hallway corner, isn't it? I will dig a big deeper into this. We might work on some alternative one-piece design then.

How about something like the Sweet Wings connection with a much larger overlap and larger splines?

Enter Myth cranks. Design dating from 2006. Weight: sub-500g including BB cups & proprietary chainrings (89g/set, blanks made by Praxis Works in '07 and further CNC'd, Ceradure coating). Patented clamping mechanism. Very very stiff, but we're still in the testing phase. If there is ever a final version, it'll differ and there's no specific release goal yet.

_________________“I always find it amazing that a material can actually sell a product when it’s really the engineering that creates and dictates how well that material will behave or perform.” — Chuck Teixeira

...Carbon spindle, ...I tried to explore a thin bearing that will fit a PF30 shell to allow a bigger spindle than 30mm. That didn't go very far. I might have to explore a larger frame BB shell. Fortunately, commercial feasibility isn't a factor, so anything goes, for brainstorming purposes....

Well, I have come across this at some point but generally I don't like outboard bearings altogether.

What it does is move the bearings outside of the BB shell to make room for the spindle. But the bearings will leave little room for crank arms. Plus the cup/BB interface will give rise to additional flex. Outboard bearings from the very beginning was an attempt to accommodate the old standard, like patch work. Now that I am making both the frame and the crank, I can indulge myself a bit more.

The million dollar question is: WHAT IS THE IDEAL DIAMETER OF A CARBON SPINDLE?

Look says 50mm, but theirs has a concave in the middle, so it will not act as a true 50mm.

What about a derlin shell that could go around the spindle non-drive side. The spindle could be tapered, and the shell would 1. act as a shim between shell and bearing. 2. be threaded to allow for preload adjustment (a la many of truvativ's pf30 specific cranks 3. be machined at the end to allow for the non-drive crank connection 4. the connection wouldn't be tapered, but act similar to the hollowtech 2 cranks in the sense of there being pinch bolts and a way to insure the arm is completely engaged with the interface.

Very nice project. Too bad you're not looking to make something that will work for all bb systems. I love my VumaQuads but on the third set of bearings and rings and plan to retire it when they wear out again. At that point I'll have about 40,000 miles on them but it seems no one has done anything real innovative with cranks for a while. My frame that will be with me for some time to come uses the "old" 68mm british standard.

The reason I am not making it compatible with all past standards is exactly the philosophy driving this effort. From an industrial designers perspective it's always better to go for the best product he can think of, before he is asked to consider commercial viability.

BSA frankly was most appropriate for steel. We have gone to 30mm spindle after several decades, which apparently is fairly suitable for alu. But I believe Carbon requires a larger spindle to make sense. THM going back to alu spindle on the M3 is evidence.

Fortunately I am putting together bike frames myself so I am going for better integration this time.

Design wise, while I dont have the answer yet, I am fairly confident I will find it. THe biggest problem is probably with carbon layup, which my engineers are less familiar with on the crank. FSA cranks are known to be soft but THM known to be fairly stiff. Must be the layup technology. Need to do more work on that front...

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